It is known to electrically couple multiple switching sub-converters in parallel to increase switching power converter capacity and/or to improve switching power converter performance. One type of switching power converter with multiple switching sub-converters is a “multi-phase” switching power converter, where the sub-converters, which are often referred to as “phases,” switch out-of-phase with respect to each other. Such out-of-phase switching results in ripple current cancellation at the converter output filter and allows the multi-phase converter to have a better transient response than an otherwise similar single-phase converter.
As taught in U.S. Pat. No. 6,362,986 to Schultz et al., which is incorporated herein by reference, a multi-phase switching power converter's performance can be improved by magnetically coupling the energy storage inductors of two or more phases. Such magnetic coupling results in ripple current cancellation in the inductors and increases ripple switching frequency, thereby improving converter transient response, reducing input and output filtering requirements, and/or improving converter efficiency, relative to an otherwise identical converter without magnetically coupled inductors.
Two or more magnetically coupled inductors are often collectively referred to as a “coupled inductor” and have associated leakage inductance and magnetizing inductance values. Magnetizing inductance is associated with magnetic coupling between windings; thus, the larger the magnetizing inductance, the stronger the magnetic coupling between windings. Leakage inductance, on the other hand, is associated with energy storage. Thus, the larger the leakage inductance, the more energy stored in the inductor. Leakage inductance results from leakage magnetic flux, which is magnetic flux generated by current flowing through one winding of the inductor that is not coupled to the other windings of the inductor.
Integrated circuits including two or more power stages have been developed for use in switching power converters. For example, FIG. 1 shows a top plan view of a prior art four-phase buck switching power converter 100 including two integrated circuits 102 and a coupled inductor 104. In this document, specific instances of an item may be referred to by use of a numeral in parentheses (e.g., integrated circuit 102(1)) while numerals without parentheses refer to any such item (e.g., integrated circuits 102). Coupled inductor 104 includes four windings 106, and opposing ends of each winding form respective first and second solder tabs 108, 110. Solder tabs 108, 110 are uniformly distributed along a length 112 of coupled inductor 104.
Each integrated circuit 102 includes two buck power stages (not shown) and two terminal sets 114. Each terminal set 114 include one or more electrical terminals, such as one or more solder balls, electrically coupled to a common node and disposed on a bottom outer surface of integrated circuit 102. Terminal sets 114 are symbolically indicated by dashed line in the FIG. 1 top plan view because the terminal sets are not visible when looking at the tops of integrated circuits 102. Each terminal set 114 provides electrical interface to a respective power stage of the integrated circuit. Both power stages and associated terminal sets 114 are located in the same portion of the integrated circuit, to ease integrated circuit design and construction. Thus, terminal sets 114 are located close together on integrated circuit 102.
Each terminal set 114 is electrically coupled to a respective first solder tab 108 by a conductor (not shown), such as a printed circuit board (PCB) conductive “trace.” Each power stage and its respective winding 106 form part of a phase of buck switching converter 100. Accordingly, each integrated circuit 102 supports a respective pair of converter 100 phases, and coupled inductor 104 supports all four phases of converter 100.